Millions of cancers are diagnosed every year in the United States. Cancer strikes more than 1/3rd of the population and accounts for more than 20% of all deaths. In addition, the economic burden of cancer is immense. Early diagnosis and treatment are vital and the identification of persons at increased risk of cancer is an important objective of cancer research. This application utilizes CGH microarray technology to [improve the detection and prognostic evaluation of breast cancer. An enhanced ability to predict the severity or aggressiveness of cancer will inevitably lead to improved interventional treatment.] The long-term objective of the research is to incorporate microarray technology into routine cancer protocols and to provide a comprehensive, multidisciplinary approach to cancer detection and treatment. The research involves paired comparison analyses of cancer patients on 2 levels. Firstly, it will compare microarray profiles of recently relapsed breast cancer patients at 2 points in time by analyzing DNA obtained from their current (flash-frozen) tumor and DNA obtained from their original (formalin-fixed, paraffin-embedded) tumor. Secondly, it will compare microarray profiles of the relapsed patients with profiles of DNA obtained from original tumors of matched patients who are still in remission during the same timeframe after initial diagnosis. Additional molecular analyses, such as Methylation-PCR and Loss of Heterozygosity testing will be performed to confirm and/or clarify microarray data. This project will take important steps towards the validation of CGH microarray technology for breast cancer detection and treatment. The aims of the project are predicated on the following hypotheses: [(1) that the profile of gene copy number abnormalities in breast carcinomas reflect its biological potential; (2) that genomic profiling has the ability to predict a subgroup of patients who are at greater risk for recurrence; and (3) that genomic profiles of breast cancer will help the clinician to provide individualized targeted therapy.] The ability to detect the [underlying molecular basis of breast cancer] and to provide sophisticated patient-specific monitoring of the efficacy of treatment is of manifest benefit to the entire U.S. population and also has broad relevance because of the incidence of breast cancer worldwide.